saeedakobiakov wrote:My car does not have icc.i meant, i got lots of hills in my area. so over the hill speed very by 3 mph.i want the car drive the speed i set it at, and not slower up the hill and faster down the hill.
Ah! Now that is a tough problem for cruise controls - hills can throw off the feedback system that keeps you at a constant speed on level ground. The steeper the hill, the slower the speed you set it at (low engine revs means less torque available), the worse the hunting.
There is no simple solution for this. The exact values used for the feedback system depend on the best compromise that the engineer can tweak into it for level ground and slopes upto a point.
What has worked for me (and also good to do for your transmission, regardless, on uphill slopes!) is to drop down to M into 4th gear - or maybe even 3rd on steep slopes - without disengaging the cruise control. This rev's up the engine and puts it into a higher power/torque range. This extra power/torque allows it to accelerate a bit more quickly uphill and use a bit more engine braking going downhill - this partially compensates for the parameters of the feedback system that would normally be more optimal for level ground.
Then the cruise control finds it easier to maintain a particular speed range - may drop from +/- 3 or 4 mph to about +/- 1 or 2 mph (depending on the slope).
There is no perfect solution here unfortunately.
Z